Apparatus for the rectification and amplification of sound waves



' H. N. JAMES, 1,829,399 APPARATUS .FOR 'THE RECTIFIGATION ANDAMPLIFICATION OF SOUND WAVES Filed June 2'7, 1930 2 Sheets-Sheet 1 Nov.3, 1 931.

Illlill Patented Nov. 3, 19 31 PATENT OFFICE HENRY NEWTON JAMES, OECHICAGO, ILLINOIS APPARATUS FOR THE RECTIFICATION AND AMPLIFICATION 01SOUND WAVES Application filed June 27,

This invention relates to improvements in apparatus for therectification and amplification of sound waves, and more particularly toa device to be used in coni'unction with any instrument for mechanica lyor electrically reproducing sound, such as the loud speaker unit of aradio receiving set or phonograph;

The object of the invention is to provide an instrument or device,having as its primary function the rectifying and clarifying ofreproduced sound waves, and thus eliminating the discordant anddistorted tones due to faulty re roduction and amplification.

A further ob ect of the invention is to provide an apparatus especiallydesigned to be used in theaters and auditoriums in which sound isreproduced, as for instance, from records and in synchrony with motionpictures by an electro-magnetic reproducer or dynamic loud speaker, andas such is intended to rectify and clarify the sound as it is projectedfrom the reproducer and then amplifying it to the proper volume forclear reception by the audience.

While the device embodying my invention is in part an amplifier of soundwaves, it is not an amplifying horn as its general shape may indicatebut, as will presently be seen, is a vibratory shell into which thereproduced sound waves are projected and through the agency of wirestuned to a true harmonic pitch scale extending throughout the full rangeof sound vibration frequencies, the true tone vibrations are againreproduced by sympathetic vibration of the wires and am lified by thevibratory walls of the shell, w ile the discordant sounds to which thewires do not respond are filtered out and thus eliminated.

A preferred embodiment of my invention is disclosed in the accompanyingdrawings in which:

Figure 1 is a general view in side elevation of the device. I

Figure 2 is a view in front elevation.

Figure 3 is a view in vertical section longitudinally of the device astaken on line 3-3 of Figure 2. I r

Figure ,4 is an enlarged detail view in ver- 1830. Serial No. 464,142.

tical section through the sound chamber, as taken on line H of Figure 3.

Fi ure 5 is an enlarged detail view showing t e manner in WhlCll thestrings of-the sound chamber are tuned.

Figure 6 is a detail view in section through a corner of the soundshell, showing the construction and method of mounting the tuned wires,and

Figure 7 is an enlarged detail view in section of fragments of the shelland the screen supporting the external groups of wires.

Referring to the device in its general aspect, the same consists of abox-like sound duct 1, square in cross-section and from 3 to '5 feet inlength and say one foot to two feet square in its internal dimensions.This duct 1 is open at both ends and at one end it connects with andopens into the apex of a pyramidal-shaped shell 2, that is, a four-sidedhollow casing diverging from a framed opening connected with the frontend of the sound duct 1 to a large framed opening about six feet square.

The device rests in horizontal position on the floor with one of theedges of the shell 2 in contact therewith, thus elevating the sound duct1 to a height of, say, 2 or 3 feet above the floor. Supporting the rearend of the sound duct is an upright member 3, and extending rearwardlytherefrom and below the opening to the duct is a shelf 4 on which reststhe sound reproducer 5 which may be assumed to be an electro-magneticloud speaker such as would be used in reproducing sound from records ora radio receiver. The cone 5a of the loud speaker 5 is directed into theopen end of the sound duct and registers with an opening 3a formed inthe upright 3, so that the sound waves emanating from the reproducer aredelivered axially to said duct. By preference the reproducer is enclosedwithin a removable housing or hood 6 supported upon the shelf, this hoodbeing a boxlike enclosure of any suitable construction having its wallslined with a heavy nap fabric such as velour. The purpose of this hoodis to absorb all sound vibrations emanating from the reproducer whichare'not desired to be transmitted into the sound chamber or passagewithin the duct.

- The sound duct 1 considered as a separate unit of the device, ispreferably constructed of wood, with walls of, say, one inch inthickness, or at least of sufficient thickness to resist vibration underthe influence of the sound waves. Moreover, the duct is preferablyconstructed in two sections, that is, a main section 1a of greaterlength adjacent the sound receiving end, and a short section 16 ad acentthe shell 2.

These two sections are joined end to end by abutting end frames 7 7,there being similar frames at the extremities of the duct, and which, aswill be presently seen, serve as the supports for banks or series ofvertical metal strings which extend across the sound chamber atintervals throughout its length. The sound duct is preferably made insections for convenience in adapting the device to auditoriums ofdifferent sizes, that is to say, a relatively small auditorium willpermit of a shorter sound duct and hence the, shorter section can beremoved without necessitating a complete reconstruction of this portionof the apparatus. However, for the purpose of this disclosure, the soundduct may be considered as a single section.

In the top wall of the sound duct and at equal and predeterminedintervals along a median line are a series of holes 8, say, of

inch in diameter, these holes being fitted with removable stops or plugs9. There are shown eight stops in the larger section Ia and two in theshorter section 16 of the sound duct. Also in the bottom walls of theduct is a vent hole 10 also provided with a stop or plug 11. It may bestated at this point that these holes are made use of in adjusting theapparatus to the particular auditorium in which it has been installed,in order to secure the best results. Thus by removing a certain stop orstops from the holes 8, together with the stop from the vent hole 10,the volume of sound passing through the chamber is diminished until itmeets the volume requirements of the auditorium as determined by itscapacity and acoustic conditions.

Adjacent each of the frame members 7 of the sound duct 1 are mountedsets or groups of parallel tuned metal strings or wlres 12 arranged toextend vertically through the interior of the sound chamber (Figures 3and 4). The strings of each group are strung between bars 14: and 15extendin transversely across the top and bottom wal s of the duct andabutting against the frames 7, said strings pbassing through small boresin the top and ottom walls of the duct and thence through or intoregistering bores 14a and 15a in the bars 14, 15 respectively. Thus thelower ends of the strings are fixed to screws 15?) anchored in the underside of the bottom bars 15, while the upper ends of the strings areattached to tuning pins 16 similar to those used on stringed instrumentsof the mandoline type. As shown in Figure 5, each string is coiled upona tuning pin consisting of a shaft 17 extending transversely of the bore14a in the bar 14, which is rotated by a worm wheel 17a on the shaft anda worm 18 on a tuning spindle 18a supported in a bracket 19 secured tothe' face of the bar 14. As shown in Figure 3, there are four groups ofeight (8) strings each, between the ends of the duct, although thenumber of groups, the

a definite note in the scale, responds to and vibrates in sympathy witha sound wave of the same frequency entering the sound chamber.

Thus, one group of strings may include the highest pitched notes,another the next lower, and so on until the full ran e is coveredbetween the higher frequency limits mentioned, the maximum of 8192cycles per second being recognized as the limit of audible reception.

Referring now to the vibrator shell 2, the same consists of asubstantial frame work including a small square frame 20 which surroundsthe central opening from the sound duct and abuts the end frame 7thereof, diverging corner frame members 21 of angle section, and a largesquare frame 22 surrounding the open end. These frame members joinedtogether, form a rigid skeleton frame of pyramid shape, and includedtherebetween are four thin walls or vibratory panels 23, which surroundthe four sides of the frame. These vibratory panels may be made of anysuitable material such as wood or a composite material having therequisite resonant qualities of a vibratory sounding board. As shown inFigure 6 these panels 23 cut to shape, are fitted at their edges intothe frames 20 and 22, and edges of the frame members 21, thus formingangularly disposed divergent walls, each forming a separate vibratoryunit.

The shell is preferably braced and reinforced externally, but sincethese are details which may be modified without affecting the functionof the shell, they need not be elaborated upon.

Extending transversely of each of these vibratory panels and within theshell are other series or groups of tuned wires 24 arranged in parallelrelation and anchored at their ends to the corner frame members 21,

that is, the wires of each group are fixed at one end to suitable pins25 anchored in one of the frame members and secured to a correspondingrow of tuning pins 26 on the frame members on the opposite side as shownin Figure 6, these tuning pins being similar to those used in pianoconstruction. Narrow bars 27 in which a bridge strip 28 is inserted, areapplied along the edges of the frame members 21 adjacent the rows ofpins 25 and 26, so that the wires are spaceda uniform distance from thesurfaces of the panels 23, and their length is defined.

Thus each frame member supports rows of fixed and tuning pins for thegroups of tuned wires on either side thereof, t ese wires beingapproximately one hundred and fifty in number, that is, about forty ineach grou and ranging from one foot to, say, five an one-half feet inlength. Moreover, the strings surrounding the interior of the shell areheavier than those within the sound chamber, and are tuned to vibrate atfrequencies between 2900 and 500. cycles per second, the shorter stringsbeing manifestly tuned to the higher frequenc pitches. Over the openingor mout of the shell 2 is a screen of tuned wires 29, which forstructural reasons are preferably supported upon a separate square frameof about the same size as the open end of the shell 2, and consisting oftwo heavy beam-like members 30 which support the. ends of the wires, anda plurality of transverse members in the form of tubular columns 31extending between the ends of the beams. The beams 30, 30 extendhorizontally in line with the top and bottom of the shell, and arefastened to the outer frame 22 of the shell 2 by suitable attachingdevices such as lag screws 32 and spacing,

sleeves 32a, (Figure 7). The strings 29 are all of the same length andpreferably divided,

into two groups on opposite sides of the beams, the same arrangement ofanchor pins 33 and tuning pins 34 being carried by the beams forsupporting the ends-of the wires.

There are about 160 wires in this screen which extend in a double rowentirely across the opening to the shell, and bein relatively heavywires and under considera le tension when tuned, demand not only aseparate frame, but their division into groups on opposite sides, inorder to equalize the stresses on the, frame and prevent its distortion.

Moreover, the frame supporting the external groups of strings is maderemovable so that access may be had to the internal groups of stringsfor tuning. And finally as in the case of the other groups of wires,these strings are tuned to the physical pitch scale, but beingrelatively heavier and longer, embrace the lower frequencies of soundwave vibrations, say, from 26 to 500 cycles per second.

Considering now the several groups of tuned strings or wires as a whole,it will be seen that they are divided into three series,

namely, those in the sound chamber of the the strings are all tuned to adifferent pitch,

although two or more strings may be tuned to the same pitch. Moreover,the tuning is in accordance with the physical pitch scale based onmiddle C, with a frequency of 256 cycles per second, and ran ing aboveand below that note throughout tl ie. range of audible frequencies.

Now, considering sound entering the sound chamber from the reproducer 5as waves or v bratory-disturbances of the atmos here of differentfrequencies, it follows t at the string or strings having the samefrequency Wlll be set in motion and vibrate in sympathy therewith,producing the same note. Thus if the sound reproduced, whether s eech ormusic, is harmonious, it will again e reproduced 1n its passage throughthe sound chamber and shell, not only in pure tones from the vibrationof the strings tuned to ing and reproduction of sound by mechanicalagencies is not altogether perfect, some of the tones being distorted,and other tones, notably those in the lower frequency range, beingsuppressed. In addition, inharmonious overtones and mechanical noisesare created in the course of reproduction and amplification, whichinterfere greatly with clear and harmonious reception. In passingthrough the apparatus, these undesirable notes, overtones and noises aremodified and suppressed to a great extent, whereas the true andharmonious notes are reproduced, amplified and brought up to theirproper volume so that the result is a harmonious bal anced whole inharmonics and chromatics.

The true sense of tone reproduction as accomplished by the use of'theapparatus is erhaps rendered more understandable by hearing in mind thatthe sound emanating from the reproducer is not the same sound whichultimately reaches the ear. In fact, the sound projected into thechamber of the apparatus is in reality only waves which set in vibrationthe tuned strings pitched to frequencies of the true physical scale sothat the source of the audible sound is the strings and not thereproducer. Consequently no sound or note which is not true orharmonious, is created and amplified for audible reception by theapparatus. Thus it will be seen that the apparatus is not a musicalinstrument on the one hand, or an amplifying horn on the other, butrather a mechanical device which receives a vast assortment of soundWaves, and functions to rectify those that are slightly off tone, tosuppress and modify those that are discordant or foreign, and finally toamplify and project the true and harmonious tones with clarity,mellowness and purity.

Having set forth a preferred embodiment of my invention, I claim:

1. In an apparatus of the character described, the combination with asound reproducer of an elongated sound chamber of uniform dimensionsadapted to receive the sound waves from said reproducer at one end, andhaving a multiplicity of strings strung transversely thereof and tunedto a predetermined pitch scale, and an amplifying shell havingvibratory'walls communieating with the other end of said chamber.

2. In an apparatus of the character described. the combination with asound reproducer of an elongated sound chamber adapted to receive thesound waves from said reproducer at one end, and having a multiplicityof strings strung transverselv thereof and tuned to a predeterminedpitch scale, and a reflecting shell having .vibratory divergent wallscommunicating with the other end of said chamber.

3. In an apparatus of the character described, the combination with asound reproducer of an elongated sound chamber open at each end andadapted to receive sound waves from said reproducer, a shellcommunicating with said chamber and having divergent vibratory walls anda plurality of tuned vibrating elements within said chamber and shelland adapted to be set in vibration by the passage of sound wavestherethrough.

l. In an apparatus of the character described, the combination with asound reproducer of an elongated sound duct of uniform internaldimensions adapted to receive the sound waves from said reproducer atone end and open at its opposite end, said duct having a series oflongitudinally spaced holes through the wall thereof, and removablestops for closing said holes communicating with said sound chamber.

5. In an apparatus of the character described, the combination with asound reproducer of an open ended elongated sound duct of uniforminternal dimension, having a series of longitudinally spaced holesthrough the wall thereof, stops normally closing said holes, and a groupof strings extending transversely of said duct and adapted to be tunedto a predetermined pitch scale.

6. In an apparatus of the character described, the combination with asound repro-' ducer of an elongated sound chamber of uniform internaldimensions, a series of longiscribed, the combination with a soundre'producer of an elongated sound chamber of uniform internal dimensionopen at one end, groups of tuned strings extending transversely of saidchamber, a sound reflecting shell arranged symmetrically about the openend of said chamber, and groups of tuned strings mounted on the innersurface of said shell.

8. In an apparatus of the character described, the combination with asound reproducer of an elongated sound chamber of uniform internaldimension, groups of tuned strings extending transversely of saidchamber and arranged in spaced relation throughout the length thereof, areflecting shell arranged symmetrically about the open end of saidchamber, groups of tuned strings mounted adjacent the inner surface ofsaid shell and tuned strings extending across the large open end of saidshell.

9. In an apparatus of the character described, the combination with asound reproducer of a sound duct having one end open to receive thesound vibration from said reproducer, a sound reflecting shell havinvibratory walls diverging from a centra opening communicating with theother end of said duct, and a frame surrounding its outer end, and amultiplicity of tuned strings extending across said frame.

10. In an apparatus of the character described, the combination with asound reproducer of a sound duct having one end open to receive thesound vibration from said reproducer, groups of tuned strings extendingtransversely of said duct, a sound reflecting shell having vibrator,walls diverging from a central opening communicating with the other endof said duct, and a screen consisting of a multiplicity of tuned strin sextending over the open end of said shel 11. In an apparatus of thecharacter described, the combination with a sound reproducer of a soundduct having one end open to receive the sound vibration from saidreproducer, a sound reflecting shell having vibratory walls divergingfrom a central opening communicating with the other end of said duct,and a frame surrounding the outer end of said shell supporting amultiplicity of tuned strings.

12. In an apparatus of the character described, the combination with asound reproducer of a sound duct having one end open to receive thesound vibration from said reproducer, groups of tuned strings extendingtransversely of said duct, a sound June, 1930.

reflecting shell having vibratory walls diverging from a central openincommunicat ing with the other end of sai duct, groups of tuned stringsextending transversely of the inner faces of said walls, and a framemounted in front of said shell and sup orting a multiplicity of paralleltuned strings.

13. In an apparatus of the character described, the combination of asound duct 9. sound reflecting shell communicating with one end of saidduct, a sound reproducer mounted at the other end of said duct, and asound absorbing hood surrounding said reproducer.

14. In an apparatus of the character described, the combination of anelongated duct having non-virbratory walls, a sound reflecting shellhaving a central opening communicating with one end of said duct andvibratory diverging walls, a support at the opposite end of said duct, asound reproducer mounted on said support, and a sound absorbing hoodenclosing said reproducer.

15. In an apparatus of the character described, the combination of asound duct adapted to receive sound waves at one end, a sound amplifyingshell communicating with the opposite end of said duct, a series oftuned strings mounted within said sound duct, and means for varying thevolume of the sound produced to the size of the auditorium in which theapparatus is located.

16. In an apparatus of the character de scribed, the combination of asound duct adapted to receive sound waves at one end, a sound amplifyingshell communicating with the opposite end of said duct, and apluralityof groups of tuned strings extending across said sound duct and spacedapart longitudinally thereof.

17. In an apparatus of the character described, the combination of asound duct adapted to receive sound waves at one end, a

sound am lifying shell communicating with the opposite end of said duct,and a plurality of groups of tuned strings extending across said soundduct and spaced apart longitudinally thereof, and means in said soundduct for varying the volume of the sound produced to the size of theauditorium in which the apparatus is located.

18. In an apparatus of the character described, the combination of asound duct adapted to receive sound waves at one end, a sound amplifyingshell communicating with the opposite end of said duct, and groups of I,

strings extending transversel of said sound duct and across the mouth 0said shell and capable of being tuned to predetermined scales.

Signed at Chicago, 111., this 24th day of HENRY NEWTON JAMES.

